If the cause of failure is *NOT* related to anything you did(overclocking, incorrect installation, etc) and it was not abused(LN2, excessive voltages, etc) then I see no issue RMA'ing it and keeping mum about certain details.

Technically aftermarket thermal paste and heatsinks also void both Intel's and AMD's CPU warrenties. Its more to cover themselves and give them a legal avenue to deny an RMA if they feel the products been abused.

Also, if they deny my RMA due to w/e reason, as long as its not a bs reason, I'll accept it. But my point is, something like lapping your CPU throws away ANY warranty you had, questionable or not.